Etching



A 27, 1943. J. J. ORMOND ETGHING File d June 50, 1941 ing members.

Patented Apr. 27, 1943 UNITED STATES PATENT OFFICE ETCHING John J.Ormond, Boston, Mass, assignor of twothirds to Joseph 1). Ramsey,Boston, Mass.

7 Claims.

This invention relates to methods of etching and more especially tomethods of engraving printing rolls.

A principal object of the invention is to improve methods of etching andto devise a procedure for more uniformly and rapidly carrying outetching operations on a printing roll. An-- other object is to provide ameans of varying and otherwise controlling etching operations. Theinvention also aims to provide a method of etching which is simple,cheap and efficient.

The nature of the invention, and its objects, will be more fullyunderstood from the following description of the drawing and discussionrelating thereto.

In the accompanying drawing:

Fig. l is a perspective view illustrating a step in the method of theinvention;

Fig, 2 is a perspective View illustrating another step in the method ofthe invention;

Fig. 3 is a perspective View illustrating still another step in themethod referred to;

Fig. 4 is a perspective View of a finished printing member; and

Fig. 5 is a detail fragmentary view in cross section.

Referring more in detail to the drawing, numeral l indicates a roll, asfor example a copper roll, of the type employed in making textile print-In accordance with the method of the invention, the roll is selectivelycovered with resist material 2, arranged to form a bare metal outline 3of a square design, and additional resist material l in the form ofspacedapart lines extending diagonally within the outline 3 to leavebare metal lines 5. The resist material is allowed to dry and in somecases exposed to heat and other agents adapted to increase theresistance of the resist to etching reagents.

The roll is covered with an absorbent blanket member 6, as for examplean absorbent cotton, which completely encircles the roll and ispreferably coated or sealed at its ends with a sealing material such asbeeswax 1.

By some suitable means as spraying, coating or dipping, the blanket 6 isimpregnated with an etching reagent such as perchloride of iron.Thereafter a pressure element 8 consisting of an inflatable tubularmember is wrapped around the blanket 6 in overlapping relation to exerta pressure on the blanket and force the absorbed etching reagent againstthe bare metal surface of the roll. The pressure of the strap is variedby inflating the element 8 through the valve 9,

to take a position such as that shown in Fig. 5. The etching reagent isthus held under pressure in contact with the roll surface for a suitableperiod, then removed, and the resist material washed away, leaving anetched outline l0 and etched ground lines I An important aspect of theinvention is the method of using an absorbent blanket member to retainor hold an etching reagent in proximity to the surface of a rollselectively covered with resist material. The absorbent blanket memberpermits the use of limited amounts of etching reagent and affords adesirable means of controlling the extent or intensity of etching, in asubstantially uniform manner, all around the periphery of the rollsurface.

The sealing material I at the ends of the blanket serves to holdabsorbed etching reagent in the blanket when pressure is exertedthereon, thus preventing the acid reagent from being squeezed outthrough the ends of the blanket and being lost or causing difficulty inany other way. It is pointed out that by tightly winding the tubularmember around the sealing material, and in overlapping relation, asubstantial sealing effeet is secured all around the blanket.

Application of etching reagents by methods other than dipping orimmersing in a bath, as for example spraying or coating, is alsofacilitated by the use of the blanket member. The use of an absorbentblanket member tends to hold a reservoir of etching reagent which iscomparable to immersing the roll in a bath of etching reagent. However,the disadvantage of undercutting resulting from immersion of a roll in abath of etching reagent is greatly modified, since the blanket tends todirect the etching reagent directly against the surface area of the rollwithout allowing the etching reagent to come into contact with the sidesof etched away portions to any appreciable extent.

In addition to the cotton cited as a suitable material for constitutingan absorbent blanket member, I may desire to employ various othermaterials such as glass wool, fibrous plastics and others. With any ofthese blanket materials, it is desirable to employ a sealing material atthe ends of the roll to prevent the etching reagent from being lost.Other waxes, in addition to beeswax, may be employed, and otherthermoplastic materials such as resins and the like, which aresubstantially impervious to the action of etching reagents, may bedesired to be employed.

Another important feature of the invention is the use of a pressureelement, preferably in the form of an inflatable tube, wound inoverlapping relation around the blanket member noted, to force theetching reagent against the surface of a roll to be etched, and also toact as a sealing member While exerting such pressure. The pressuremember serves as a means of applying pressure uniformly at all pointsaround the periphery of a roll. This pressure quickens the etchingaction of etching reagents in a manner similar to the increased speed ofetching commonly obtained by blast etching. It is pointed out that blastetching cannot be readily carried out at all points around the surfaceof a roll. The combined action of an absorbent blanket and pressuremember provides an intensive etching action which is not readilyobtained in other ways and the method of forcing acid through anabsorbent blanket also tends to prevent undercutting to a verysubstantial degree.

The inflatable tube not only affords a means of increasing the pressureobtained by winding a strip around the blanket, but also provides ameans of varying pressure as for example by intermittently increasingand decreasing the pressure. This variation in pressure is desirable insome types of etching work and makes available a control not heretoforeavailable in etching procedures.

While I have shown an inflatable tube with means for inflating thismember so as to vary the pressure which ma be exerted all around theroll surface, it should be understood that various other types ofpressure members may be desired to be employed, as for example aresilient sleeve which maybe supported around th blanket in variousWays, as for example clamping and the like. The method described mayalso be employed in etching various other materials than metals, as forexample glass and and like, and the pressure member may be desired to beprotected from the etching reagent by the use of materials which aresubstantially resistant to such etching reagents. The square outline I0and ground lines I I are intended to be illustrative of various designsof the type commonly employed in printing textiles, and these designsmay occur in repetition throughout the surface of the roll and injuxtaposed relation, in some cases, to provide for multicolor printing.

It will be seen thatthe method of the invention provides a desirablecontrol for carrying out etching operations, makes possible greateruniformity, avoids undercutting, is faster, and more economical.

While I have shown a preferred embodiment of the invention, it should beunderstood that various changes and modifications may be resorted to, inkeeping with the spirit of the invention as outlined by the appendedclaims.

I claim:

1. An improved method of engraving which comprises selectively applyingresist material on a surface to be engraved, mounting an absorbentmaterial over the surface to be engraved and the resist material,introducing an etching reagent into the absorbent material, thensuperimposing over the absorbent material a pressure element andresiliently urging the pressure element against the absorbent materialfor the purpose of forcing acid against the surface to be engraved.

2. That improvement in methods of engraving printing rolls whichcomprises applying resist material in selective amounts on a surface ofthe roll, then securing an absorbent material around the roll,introducing an etching reagent in the absorbent material, then windingan inflatable tube around the absorbent material, and then inflating thetube to exert pressure against the absorbent material and force theetching reagent against the surface of the printing roll.

3. That improvement in methods of engraving a printing member whichcomprises applying a resist material in selected areas on a printingmember to be etched, securing an absorbent blanket adjacent the surfaceof the printing member, sealing the ends of the absorbent material witha material which is resistant to the etching reagent, introducing anetching reagent into the blanket member, and then compressing theblanket to force the acid into those surfaces of the printing memberwhich are not covered by the resist material.

4. That improvement in methods of etching which comprises applying anetching reagent to a surface to be etched by inflating a pressureelement having an etching reagent disposed between itself and thesurface to be etched.

5. That improved method of engraving which comprises applying over amember to be engraved a blanket member, sealing the edges of the blanketmember with an agent adapted to resist attack b an etching reagent,incorporating. an etching reagent into the blanket, and then applyingpressure simultaneously over the entire surface of the blanket.

6. That improvement in methods of etching rolls which comprises applyinga resist material in selective amounts over the roll surface, thenwrapping a blanket member around the roll surface, said blanketextending from end to end of the roll, applying a liquid agent adaptedto resist etching reagents over the ends of the roll and also over theedges of the blanket, incorporating an etching reagent into the blanket,then superimposing about the blanket a pressure member for the purposeof exerting pressure on the blanket, thereby to facilitate etching ofthe roll.

7. That improvement in methods of engraving a printing roll whichcomprises applying a, resist material in selected areas of a printingmember to be etched, securing an absorbent blanket adjacent the surfaceof the printing member, introducing an etching reagent into the blanketmember and then applying pressure simultaneously over the entire surfaceof the blanket to force the etching reagent into contact with thosesurfaces of the printing member which are not covered by the resistmaterial.

JOHN J. ORMOND.

